Friday is July 4, otherwise known in the U.S. as the Fourth of July. Independence-celebrating Americans are accustomed to gazing upon red-glaring rockets, air-bursting bombs, and other shows of pyrotechnic pomp — but this year, many fireworks shows may lose their sparkle. Because of drought conditions, many shows across the country have been canceled, and several places will impose fines on backyard detonations as well. In California, where lightning-sparked wildfires are raging, Gov. Arnold Schwarzenegger told residents this week, “Don’t buy the fireworks, don’t go out and play with fireworks, because it’s just too dry and too dangerous to do those things.” Other municipalities, struggling with the tight economy, are canceling shows simply because of cost — a February explosion that engulfed 20 Chinese fireworks warehouses has severely curtailed supply, driving up prices by nearly 20 percent.